This invention relates generally to a remote control system for a mobile X-ray unit and particularly to an electromagnetic exposure switch system for mobile X-ray units that permits rotor preparation and exposure activation of a radiography system.
X-ray units take various forms depending on their intended applications. The vast majority of the units in use today are for medical diagnostic imaging of the human body. These systems are located in hospitals, clinics, and other medical facilities and are usually fixed or stationary installations. These systems are generally installed in lead lined rooms where control of the system takes place from behind a lead lined barrier, thus providing a shielded environment which minimizes the radiation exposure to a facility's X-ray technologists, patients, visitors and other personnel. These systems are also characterized as either having the ability to perform real time imaging which is known as fluoroscopy and/or single exposure filming which is known as radiography. A head-activated fluoroscopic control for the operation of X-ray fluoroscopic units is disclosed in U.S. Pat. No. 4,975,937, dated Dec. 4, 1990, to Horton, et al.
Mobile X-ray units are characterized as movable X-ray systems used to perform radiographic only studies outside of the shielded environment of an X-ray room. These systems are used throughout hospitals in the operating rooms, intensive care units, emergency rooms, or wherever they are needed to perform a study on a patient who cannot be otherwise brought to the X-ray department. U.S. Pat. No. 3,790,805, dated Feb. 5, 1974, to Anthony J. Federaro, describes one type of mobile X-ray unit.
Portable X-ray units are characterized as transportable X-ray systems used to perform radiographic only studies outside of the hospital environment. They tend to be lighter in weight and are easily dismantled which enables the system to be transported in an automobile. These systems are often used to perform radiographic studies in a patient's home. U.S. Pat. No. 4,170,735, dated Oct. 9, 1979, to Codina, et al., describes such a system.
The terms mobile and portable, are often used interchangeably to describe an X-ray system whose primary characteristic is to perform radiographic examinations of patients away from a fixed shielded environment. Operation of X-ray systems of these types require the area to be cleared of all personnel and the technologist to be as far as possible from the equipment during the taking of an X-ray, to minimize potentially harmful radiation exposure.
Whether the X-ray unit is stationary, mobile or portable it will frequently use X-ray tubes whose anode structure is a rotating disc. Specifically, an X-ray tube is a vacuum tube diode type device possessing a cathode structure separated from an anode structure. U.S. Pat. No. 4,225,787, dated Sep. 30, 1980, to Shapiro, et al., explains the operating requirements of an X-ray system employing a rotating anode X-ray tube. Generally speaking, prior to taking an X-ray exposure, the cathode is heated to the required temperature, and the anode is simultaneously "boosted" to the proper rotational speed. A predetermined fixed time interval is allowed for the cathode to heat and for the anode disc to accelerate. When the fixed time interval has elapsed, and when the system receives the exposure command, high voltage is then applied between the anode and the cathode which will subsequently cause the tube to generate X-rays.
The above described X-ray units possess electrical circuits activated by an exposure switch to control the necessary X-ray tube functions needed to make a radiographic exposure. Specifically, X-ray machines which employ a rotating anode X-ray tube have an exposure switch which is comprised of a double set of electromechanical switches. The first electrochemical switch includes a set of contacts coupled to the rotor circuitry to affect the rotation of the anode and the heating of the cathode. Once the anode reaches the desired speed and the cathode is heated, a second electromechanical switch includes a set of contacts coupled to the exposure circuitry so that activation of the second set of contacts will initiate a radiographic exposure with no further delay.
Exposure switches for X-ray units can take various forms. Although their configurations may vary, the exposure switches of mobile and portable X-ray units are connected to the unit by an electrical cable of limited length. U.S. Pat. No. 4,170,735, dated Oct. 9, 1979, to Codina, et al., discloses a portable X-ray unit having a hand held remote control mechanically and electrically connected to the X-ray unit by a cable. A remote control exposure switch connected by a cable of a limited length suffers many disadvantages as the X-ray technologist endeavors to get as far away as possible from the machine during the actual taking of an X-ray exposure. The lack of an X-ray shielded environment during the taking of a mobile or portable X-ray exposure necessitates this procedure to minimize the harmful effects of accumulated doses of ionizing radiation received by the X-ray technologist.
Many potentially unsafe incidents can occur when conventional exposure switch cords are extended. For example, when extended, the exposure switch cord can topple an intravenous pole, dislodge a catheter, interfere with monitoring electrodes, respirators, or other forms of life support equipment.
Another disadvantage is that, when extended, these cables are subjected to mechanical stress. Mechanical stress to the interconnecting electrical cable often results in this cable being cut or frayed which can result in shorted or open electrical connections. Cut cables can present a shock safety problem while a shorted cable can cause serious damage to the rotating anode X-ray tube. Yet another disadvantage of previous X-ray exposure switches is they require the continuous activation of a plurality of electrical switches to prepare the rotating anode X-ray tube and create a radiographic exposure. The problem with these types of switches is that the multiple electromechanical switch mechanisms often jam. Jammed switch mechanisms which go undetected can cause excessive heat to build up in the X-ray tube and create a severe safety problem. Still another disadvantage of faulty electrically connected X-ray exposure switches is that they can cause incomplete exposures which necessitate retakes or unwarranted exposures, which expose both the technologist and patient to unnecessary potentially harmful radiation. Accordingly, an electromagnetic remote control exposure switch system for a mobile X-ray unit which is safe to use from a patient perspective and from a technologist perspective and that overcomes the disadvantages noted above, is desired.